Three Silent Failures Rubber Duck Caught
All three slipped past the main model's self-reflection — and pass tests cleanly
The proposed scheduler was designed to start and immediately exit, running zero jobs. On top of that, one of the scheduled tasks was an infinite loop.
Duck caught → A broken startup lifecycle plus an infinite loop — two structural defects in a single proposal.
Silent failure pattern: Scheduler exits with code 0. No error log.
A loop silently overwrote the same dict key on every iteration, dropping three out of four Solr facet categories from every search query. No errors raised.
Duck caught → 75% of search facets silently missing — data loss without any runtime error.
Silent failure pattern: Search results return, but facets are incomplete. Tests still pass.
New code stopped writing to a Redis key while three other files continued to read from it. The email confirmation UI and cleanup paths would have silently broken in production.
Duck caught → Three files still reading a key that no one writes anymore — silent damage across file boundaries.
Silent failure pattern: No deploy-time error. Email confirmation quietly stops working days later.
Common pattern across all three
None of them raises a runtime error. Tests pass, deploy succeeds, and the feature silently breaks. This is exactly the category self-reflection cannot catch — and where a model with a different perspective is most valuable.
Source: GitHub Blog "GitHub Copilot CLI combines model families for a second opinion" (April 6, 2026)